I've been trying to save up space and for this reason I'm using the "don't keep copies of any messages" option.

I was thinking though, can I instead choose to save all emails and attachments, but an external hard drive? I'd like the best of both options: when hard drive is not connected it behaves exactly as "don't keep copies of any messages", when connected it has the possibility to search all mail.

Apple seem to want me not to find where mail is stored, and does not have an option in the preferences to do what I want (that I'm aware of).

Is there anything else we can do to help you solve this?
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bmike♦Mar 29 '13 at 14:23

May I ask if anyone is using this with the latest version of OS X 10.9.4 and has anyone migrated to the latest and greatest beta with this configuration and it still works? With the new enhanced version of DropBox being 1TB I'd like to store my mail on DropBox for additional backup capabilities to enhance Time Machine.
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user89085Aug 29 '14 at 2:58

3 Answers
3

Keeping copies of your mail or anything else on your computer on an external hard drive is trivial, and why Apple has decided to make things difficult, to hide what was once common knowledge is, ironically, part of their effort to make things easy.

If the User Library is set to invisible, then Apple figures beginners can't go to ~/Library/Mail/ and delete all their mail, and Apple will get fewer support calls.

Your Mail folders are in there, and are yours to drag and drop, copy and paste, use a backup or clone app--whatever--to the location of your choice.

And everything is searchable--every last item, on your machine and externals--with the free EasyFind by DevonTech.

I was thinking of using the option in mail to store everything on my computer but then use a hard link to point to an actual folder on an external hard drive. I'm only afraid that this way when the external is not connected I won't be able to use mail period.
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John SalvatierrezDec 10 '12 at 7:44

The answer by Zo219 is nice for having two copies, but my solution is to link the folders where Mail wants to store the files to the external drive and not have two copies.

Here are the folders you'll need to have located off the main drive:

~/Library/Mail

~/Library/Containers/com.apple.mail/Data/Library/

Since the volumes are separate, you can't hard link and instead need to soft (sum) link the folders or use Finder's alias function once you've moved these folders to your second drive.

That is one way that works, but I think he wants something more seamless like a remapping of the Mail directory (~/Library/Mail) to a live clone on the external drive. I've a relative small SSD on my air (128GB) so had used a simple alias to relocate my Mail library to an external HDD at my desk. I used an alternate user "mobile" so I could check email Mail with ease when I was away from the home office. This recently broke under my current version of Mountain Lion (10.8.2) and I am currently looking at a workaround. To my knowledge, hard-linking under recent versions OS X is not for the faint of heart, as it may create difficulties with Time Machine et al. Let me know in the comments if my solution is confusing. As far as your concern about behaviour when the external drive is not connected and you launch Mail, it just quietly fails with a polite error message about no access to an unmounted target.

I use Symbolic Links. This can be done from the command line or else fram a contextual item in Finder

One program that adds this contextual item can downloaded from here Follow the instructions in the download in order to install it.

First of all copy your mail to the external location. You'll need to copy both the Mail and Mail Downloads folders which are located in ~/Library If you cannot get to that folder, in the Finder, click on the Go menu, and then Go to Folder. Then type ~/Library and hit Enter to open the folder and copy the folders. Once you have copied the folders, verify that the Mail Application is completely closed. Delete the Mail and Mail Downloads folders from the ~/Library folder. Now right click on the Mail and Mail Downloads folders in your external drive, Select Services, and then make Symbolic Links for them. Move the Symbolic Links you just created (they look like aliased folders) into ~/Library. Now rename them to be Mail and Mail Downloads. That's it!

It's important to note that if you try running the Mail Application without your external drive, you'll need to repeat all this, because without the external drive, the Mail Application will try to recreate empty Mail and Mail Downloads folders, and it may also reset your accounts in Mail.